U.S. Pat. Nos. 5,5645,241 granted to Mathias et al on Oct. 15, 1996 entitled “Convergent End Effector” and 5,579,998 granted to Hal et al on Dec. 3, 1996 entitled “Method For Coating A Substrate With A Reinforced Resin Matrix” of which the inventor Jack G. Scarpa is a co inventor and which these patents and this patent application are commonly assigned. Both of these references disclose a spray gun that utilized a nozzle that is designed to configure the spray emitted by the nozzle into an atomized convergent plume of liquid resin and targets the plume with reinforced filler material downstream of the nozzle to mix and wet the filler just prior to being applied to the surface of the substrate. In other words the reinforcing material is entrained around the atomized liquid resin flow and is caused to be captured thereby, mix therewith and become an homogeneously wetted coating material that after impact with the substrates becomes cured into a substantially reasonably thick coating exhibiting good strength and resistance characteristics. The gaseous transport stream together with the eductor deliver the ingredients in the proper proportions and the air stream for causing the atomization and mixing to provide the proper amounts of material to assure that the coating is uniform and consistent. Heating is applied in the proper sequence to assure that the viscosity is at the proper level to assure evenness of flow and better atomization.
As one skilled in this technology would appreciate, the heretofore known spray application equipment for spraying of highly loaded paints and coatings which require the addition of a high volume of solid large granular materials such as cork, glass microspheres, granular or powdered materials in the 3 to 300 microns range require large amounts of solvents to dilute solid contents down to a level where it can be sprayed effectively. This, of necessity, requires special spray equipment designs that need to be significantly large in order to effectively spray these materials. Such systems have heretofore been designed to operate in a room or compartment that include a robot that was programmed to hold the spray gun and apply the spray. An additional room housed the supply of materials to be mixed and sprayed, the various valves, hoppers, proportioning devices and the like and separated from these rooms was a room that housed the computer equipment that served to control the various valves, proportioning devices etc, to automatically effectuate the spraying.
Co-pending patent application Ser. No. 08/994,768 filed by Scarpa et al on Dec. 19, 1997 entitled “Portable Convergent Spray Gun For Applying Coatings” and also commonly assigned, exemplifies a convergent spray gun that is made into a portable unit. Like the spray guns described in the aforementioned patents which are typically held by a robot, it, likewise, is very large and as a matter of fact requires the spray apparatus to be formed as part of a wand that requires two hands to operable effectively.
These special very large spray equipment designs leads to very low actual transfer efficiencies for spraying these coating materials. These low transfer efficiencies have a significant impact on the quantities of materials, solvents and volatile organic compounds that are released into the environment. As one skilled in this technology will appreciate, from an ecology standpoint these conditions are not preferred as is recognized by the Environmental protection Agency and Occupational Safety and Health Administrations that are tightening regulations that mandate change.
While one would normally expect that in order to reduce the size of the gun and attain all of the features and particularly be able to apply the same amount of coating for each pass, one would merely have to reduce the size of each of the components of the heretofore known guns as for example, of the type exemplified in the aforementioned patents. However, merely reducing the size of the components will not realize a convergent spray gun that will effectively spray a coating and as a matter of fact such a design fails to meet the specifications for coatings that are required in the larger guns that are exemplified by the aforementioned patents and patent application. As a matter of fact, we have found that it was necessary to add additional components in order to reduce the overall size and weight of the gun so that it could be hand-held, that is, held by one hand in the same way that a commercially available paint spray gun is handled. This invention contemplates adding a concentric tube construction to the commercially available (modified to meet the needs of the present invention) spray nozzle, such as spray nozzles produced by Binks, Fanklin Park, Ill. and Graco, Detroit, Mich. that provides an inner tube that transports the resin and an outer tube that transports the air for atomizing the mixture and the dry powdered nozzle and its convergent cap. This arrangement of the concentric tubes allows the dry powdered nozzle that transports the dry powder material into a manifold to be propelled into the resin/air atomization plume. The dry granular materials and atomized resins become entrained at this point and thoroughly mix together outside the gun before being deposited on the substrate.
As is the case of the structure in the U.S. Pat. No. 5,307,992 granted to Hall et al on May 3, 1994 entitled “Method And System For Coating A Substrate With A Reinforced Resin Matrix” and commonly assigned, the U.S. Pat. No. 5,5645,241 patent, supra and the U.S. Pat. No. 5,579,998, supra, the present invention described in this patent application does not change the basic operation principles but provides a mini-gun that is capable of being hand-held for coating operations and is an improvement in ergonomic design over heretofore convergent types of guns. As mentioned above, the gun made in accordance with this invention, is also capable of use in a fully robotically automated system of the type already in operation and also can be used for incorporation for completely portable convergent nozzle spray gun systems.
What is afforded by this invention and not by way of limitation are the following features:                1) Solventless application of thermal protection coatings;        2) Compatible with solvent borne epoxy, polyurethane, silicate, waterbased or 100% solid resin symptoms;        3) Ability to accurately control thickness of applied coatings by robotics or hand-held;        4) Ability to control dimensions of area to be coated;        5) Ability to control both dry filler and resin filled material independently;        6) Enhanced ability to apply coatings to smaller parts and enclosures;        7) Ability to reduce the required passes to attain the desired thickness;        8) Significant reduction in waste and hazardous materials;        9) Significant reduction in solvents; and        10) Ability to control density.        